Development for the next generation of ISFS with 100 systems

Title: CentNet: NCAR’s Next Generation Surface Flux System

The sources and sinks of most quantities carried by the atmosphere are at the Earth’s surface (land or water).  Heat and friction at the ground control air movement. Carbon dioxide enters and exits the atmosphere through the ocean surface and plants on land. Mercury, dust, and other pollutants are moved by the near-surface wind. All of these processes can be measured directly, however this is complicated since air flow near the surface is turbulent.  Furthermore, turbulence is known to be affected by even small variations in terrain and surface characteristics.

In order to understand the effects of specific landscape features (e.g. coniferous forests in mountains), observations need to be made at many locations and over a wide range of spatial scales.  Thus, observations are required at a large number locations.

EOL has responded to this challenge by designing a new system –- CentNet -- capable of being deployed to 100 locations with thousands of measurements.  Wireless communications, MEMS technology sensors, solar power, and internet software tools are being used to enable system deployments at this scale.  The development process has involved laboratory and field testing of commercial instruments and creation of new instruments needed to meet CentNet’s ambitious goal.  Data communication, power, and mechanical infrastructure have all been designed and tested.  CentNet leverages existing EOL software tools for data acquisition, quality-control, and display.


  • Climate research: map air-ecosystem exchange of CO2 and water, measure variation of light interception by leaves
  • Meteorology: support development of numerical model parameterizations, especially treatment of surface and turbulence
  • Urban meteorology: determine dispersal of pollutants, including variation with time and location
  • Wind energy: study site wind energy potential, turbulence loading on blades, effect of wake on agriculture
  • Agriculture: measure crop productivity, water use
  • Hydrology: document patterns of rain and snowfall and how water evaporates to the atmosphere and moistens the ground



CentNet allows measurements at an unprecedented range of spatial scales, while retaining key features of our current Integrated Surface Flux System (ISFS), including:

  • Direct measurement of turbulence (that needs few assumptions)
  • State-of-the-air measurement quality
  • Siting flexibility to meet research requirements
  • Permanent storage of every data sample

CentNet also will expand existing capabilities by featuring CO2 and visible and infrared light measurements at every location.



The core CentNet measurements and sensors are:

  • Wind using 2-D sonic anemometers to resolve winds under 0.10 m/s and operate in freezing conditions
  • Temperature/Relative Humidity using EOL's aspirated sensor
  • Pressure (ambient, some with resolution to measure turbulent fluctuations)
  • Precipitation (liquid and frozen)
  • Turbulence and atmosphere/surface exchange fluxes using 3-D sonic anemometers
  • Water vapor/Carbon dioxide fluxes using open-path infrared-absorption sensors
  • Radiation resolving incoming/outgoing longwave and shortwave radiation
  • Soil heat flux using a suite of moisture, temperature profile, heat flux, and thermal properties sensor in the top 5cm of soil
  • Leaf wetness to detect moisture from dew or light precipitation
  • Video camera to document changes in surface characteristics

Other sensors added as funding allows



  • CentNet is guided by an advisory committee consisting of NCAR and University scientists representing the above applications.
  • The University of Arizona cosmic-ray soil moisture system (COSMOS) and NCAR’s ACOM/ACCORD program both have expressed interest in supporting sensors to be deployed with CentNet.
  • The National Ecological Observatory Network (NEON) has collaborated on data system design and plans to collaborate on sensor  calibrations.